Chapter 12

Question 1

What percentage of the Sun’s mass must a star be to be able to fuse hydrogen?

Answer 1

Must be at least 8% of the Sun’s mass (or 80 times Jupiter’s mas)

Question 2

What are stars below to mass of 8% of the Sun’s mass called?

Answer 2

Brown dwarfs

Question 3

What are the two properties on which we can base the differentiation between small star and large gas planets?

Answer 3

Either their formation or mass

Question 4

What are two reasons why exoplanets are impossible to see with current technology?

Answer 4

They are too dim and they orbit too close to their parent stars

Question 5

What is the detection method astrometry?

Answer 5

Measuring the wobble induced in the plane-of-sky motion of the star by the planets by observing its position over time

Question 6

What is the main difficulty with the detection method astrometry?

Answer 6

Our current technology is not accurate enough to detect wobbles at far distances

Question 7

What is the detection method pulsar planets?

Answer 7

Planets being found orbiting pulsars, by detecting the changes is the very regular pulses

Question 8

What is the detection method transit?

Answer 8

Planets observed at inclinations near 90 degrees will pass in front of host stars, dimming their light

Question 9

What is an observational challenge with the detection method transits?

Answer 9

The volume of sample, and time it takes for each transit, means tedious to preform

Question 10

As of 2015, how many potential exoplanets had been found and how many of those have been confirmed by Kepler telescope?

Answer 10

4202 potential planets and 1002 confirmed

Question 11

What is the detection method microlensing?

Answer 11

A planet can actually produce a brightening (rather than dimming) of a background star by bending the light with its gravity well

Question 12

How many detection of small planets far from their star have their been from mircolensing?

Answer 12

34 detections so far

Question 13

What is the detection method radial velocity?

Answer 13

The planet’s gravity pulls its hosts star back and forth in its orbit causing the light to be blueshifted and redshifted

Question 14

What was the first star discovered around a sun-like star and what method was used?

Answer 14

51 Pegasi B was discovered using radial velocity method

Question 15

Why is 51 Pegasi B the prototypical “hot Jupiter”?

Answer 15

It has a greater radius, but lower mass that Jupiter, and orbits extremely close to its parent star and is therefore super heated to 700 K

Question 16

What are some observational challenges associated with detection method radial velocity

Answer 16

Required high-precision repeatable spectroscopic measurements of Doppler shifts to approx 1 m/s accuracy

Question 17

To what kind of exoplanets is the detection method radial velocity most sensitive?

Answer 17

Massive planets that orbit near their stars

Question 18

What is the detection method direct detection?

Answer 18

There are two ways to directly detect the light from planets; 1. remove the starlight before imaging, 2. remove after (using models of stellar evolution)

Question 19

What method is used to directly image exoplanets?

Answer 19

Adaptive optics

Question 20

What is a coronagraph?

Answer 20

The method used to cover starlight will direct imaging exoplanets

Question 21

What is Metallicity?

Answer 21

The abundance of element heavier than He relative to the Sun

Question 22

Why is it that many more large exoplanets have been found compared to small exoplanets?

Answer 22

Solely because large planets are easier to detect

Question 23

What is the outstanding problem in the study of exoplanets?

Answer 23

The fact that we find so many large exoplanets orbiting so close to their stars contradicts our understanding of the formation of our on SS

Question 24

Why have we found so many exoplanets orbiting very close to their stars?

Answer 24

Because we have only been surveying since 1988 (ex. Saturn takes 30yrs to orbit and therefore would have been detected yet)

Question 25

What are the 4 components an exoplanet must have in order to be considered “Earth-like”

Answer 25

1. moderate temperature, 2. liquid water, 3. organic molecules, 4. energy available

Question 26

What is the habitable zone?

Answer 26

The “appropriate region” (can simply and vaguely defined as “where water can exist”)

Question 27

Is the habitable zone in the same place for all planets in an SS?

Answer 27

No, it can vary with all the individual properties of a planet

Question 28

How is the habitable zone of an SS dependent on the star?

Answer 28

Brighter stars have wider, further out HZs, while low mass stars have thinner, closer HZs

Question 29

Can the HZ change locations over the life of a star?

Answer 29

Yes, usually a star increases in luminosity throughout its lifetime, therefore expanding the HZ